Sorry, very late response since I had other matters to attend to.
Question 1:
A: Incorrect; if that was the case, on day 1, the price would be 150. Instead here, according to the graph, on day 1 the price is 30.
B: Incorrect; the slope, or rate of change, is 30.
[Note: To calculate the slope, we can take two points (I've chosen points (1,30) [1] and (2,60) [2] for you) and use the formula

.

⇒

.

= x, therefore

= 30.]
C; Correct; each day the price increases by (+) 30.
D: Incorrect; the line does not show a constant decrease, but instead a constant increase.
Question 2:
A: Most likely this answer choice. The equation seems to be in slope-intercept form on accounting that the equation has mx and b. M has the x directly after it while the b is a number that stands alone. [Note: Numbers that stand alone and without a variable are constants.] B stands for the y-intercept/initial value, or amount started with.
In short:
Q1: C
Q2: A